Forums

"Random" Circuit Needed.

Started by Jim Thompson April 1, 2015
On Thu, 16 Apr 2015 20:07:46 -0400, rickman <gnuarm@gmail.com>
wrote:

>On 4/16/2015 4:46 PM, John Fields wrote: > >> If you need the extra state, then even for huge counters the >> practicality fades into insignificance. >> >> John Fields >> > >I'm not sure what that means. Practicality is *always* an issue that >needs consideration. The primary point of LFSRs is that they can be >built to run quickly and take of little space because of the minimal >logic requirements. If you throw that away you can start looking at a >much larger field of contenders.
--- What it means is that arranging the feedback to convert a maximal length (2^n)-1 LFSR into a PRSG with a count length of 2^n is trivial compared with other methods. Can you post a contradictory example culled from the "larger field of contenders" ? John Fields
On Thu, 16 Apr 2015 10:47:36 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:


>These are electronics newsgroups.
--- And, as such, your narcissistic off-topic garbage has no proper place here. ---
>We do seem to have a faction of >ancient cackling farts who only want to gossip and whine about >personalities, and drone out insults, and haven't touched a soldering >iron in years, or decades.
--- Some of us have progressed past the soldering iron stage and have come to understand our own and others' personality defects, are working on them, and aren't afraid to talk about them. Some of us haven't. ---
>Decide where you want to stand.
--- And/Or acquiesce to the showers as your final solution? ---
>Are Fields and Sloman the people you want to be allied with?
--- Wow. Sounds like you're drawing a line in the sand with you on one side and Bill and I on the other. Why would you do that? ---
>Excuse me, I have some electronics stuff to do.
--- You're excused; go do it. John Fields
On 4/16/2015 11:25 PM, John Fields wrote:
> On Thu, 16 Apr 2015 20:07:46 -0400, rickman <gnuarm@gmail.com> > wrote: > >> On 4/16/2015 4:46 PM, John Fields wrote: >> >>> If you need the extra state, then even for huge counters the >>> practicality fades into insignificance. >>> >>> John Fields >>> >> >> I'm not sure what that means. Practicality is *always* an issue that >> needs consideration. The primary point of LFSRs is that they can be >> built to run quickly and take of little space because of the minimal >> logic requirements. If you throw that away you can start looking at a >> much larger field of contenders. > > --- > What it means is that arranging the feedback to convert a maximal > length (2^n)-1 LFSR into a PRSG with a count length of 2^n is > trivial compared with other methods. > > Can you post a contradictory example culled from the "larger field > of contenders" ?
I don't see where you have provided any examples to contradict. -- Rick
On 2015-04-16, rickman <gnuarm@gmail.com> wrote:
> On 4/15/2015 7:38 PM, John Fields wrote: >> On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson >> <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>> On Thu, 02 Apr 2015 18:52:57 -0500, John Fields >>> <jfields@austininstruments.com> wrote: >>> >>>> On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>> >>>>> On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>>>> wrote: >>>>>> >>>>>>> On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>>>> <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>>>> >>>>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>>> >>>>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>>>> twist... >>>>>>>>>> >>>>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>>>> >>>>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>>>> >>>>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>>>> device in my PSpice library. >>>>>>>>>> >>>>>>>>>> Thanks in advance. >>>>>>>>>> >>>>>>>>>> ...Jim Thompson >>>>>>>>>> >>>>>>>>> >>>>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> >>>>>>>>> Phil Hobbs >>>>>>>> >>>>>>>> I just need semi-random enough to test a fast AGC. >>>>>>>> >>>>>>>> ...Jim Thompson >>>>>>> >>>>>>> there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>>> 'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>>> appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>>> the bias point to continually drift high. >>>>>> >>>>>> I was wondering about that myself... I'll see if there's a cure. >>>>> >>>>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>>>> >>>>> not that i'd want to build it using 74LS logic. >>>> >>>> --- >>>> But, if you had to, what would it look like, schematic-wise? >>>> >>>> John Fields >>> >>> <smirk>:-} >>> >>> ...Jim Thompson >> --- >> Amazing, isn't it? >> >> Idiots with opinions post their garbage as if it was holy but post >> no evidence to support their claims. > > I don't know that Jim is an idiot, but I'm not sure this formula is very > useful to implement in logic easily. The multiply is not too bad and > the addition is easy. But the modulo operation by 2^16+1 is downright > hard. I think that is why he is smirking. He knows this is not very > practical...
The modulo is easier than the multiply. one 16 bit - 7 bit subtract one 16 bit + 0 bit add with carry. -- umop apisdn
On Fri, 17 Apr 2015 00:35:00 -0400, rickman <gnuarm@gmail.com>
wrote:

>On 4/16/2015 11:25 PM, John Fields wrote: >> On Thu, 16 Apr 2015 20:07:46 -0400, rickman <gnuarm@gmail.com> >> wrote: >> >>> On 4/16/2015 4:46 PM, John Fields wrote: >>> >>>> If you need the extra state, then even for huge counters the >>>> practicality fades into insignificance. >>>> >>>> John Fields >>>> >>> >>> I'm not sure what that means. Practicality is *always* an issue that >>> needs consideration. The primary point of LFSRs is that they can be >>> built to run quickly and take of little space because of the minimal >>> logic requirements. If you throw that away you can start looking at a >>> much larger field of contenders. >> >> --- >> What it means is that arranging the feedback to convert a maximal >> length (2^n)-1 LFSR into a PRSG with a count length of 2^n is >> trivial compared with other methods. >> >> Can you post a contradictory example culled from the "larger field >> of contenders" ? > >I don't see where you have provided any examples to contradict.
--- I already posted a link to an 8 bit PRSG with 256 output states. Did you miss it? John Fields
On Thu, 16 Apr 2015 23:14:35 -0500, John Fields
<jfields@austininstruments.com> wrote:

>On Thu, 16 Apr 2015 10:47:36 -0700, John Larkin ><jlarkin@highlandtechnology.com> wrote: > > >>These are electronics newsgroups. > >--- >And, as such, your narcissistic off-topic garbage has no proper >place here. >--- > >>We do seem to have a faction of >>ancient cackling farts who only want to gossip and whine about >>personalities, and drone out insults, and haven't touched a soldering >>iron in years, or decades. > >--- >Some of us have progressed past the soldering iron stage
Now that's really sad. What do you do all day, argue and whine on newsgroups? I'm collected some parts and am headed for the Metcal. Whine on! -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On 4/17/2015 9:11 AM, John Fields wrote:
> On Fri, 17 Apr 2015 00:35:00 -0400, rickman <gnuarm@gmail.com> > wrote: > >> On 4/16/2015 11:25 PM, John Fields wrote: >>> On Thu, 16 Apr 2015 20:07:46 -0400, rickman <gnuarm@gmail.com> >>> wrote: >>> >>>> On 4/16/2015 4:46 PM, John Fields wrote: >>>> >>>>> If you need the extra state, then even for huge counters the >>>>> practicality fades into insignificance. >>>>> >>>>> John Fields >>>>> >>>> >>>> I'm not sure what that means. Practicality is *always* an issue that >>>> needs consideration. The primary point of LFSRs is that they can be >>>> built to run quickly and take of little space because of the minimal >>>> logic requirements. If you throw that away you can start looking at a >>>> much larger field of contenders. >>> >>> --- >>> What it means is that arranging the feedback to convert a maximal >>> length (2^n)-1 LFSR into a PRSG with a count length of 2^n is >>> trivial compared with other methods. >>> >>> Can you post a contradictory example culled from the "larger field >>> of contenders" ? >> >> I don't see where you have provided any examples to contradict. > > --- > I already posted a link to an 8 bit PRSG with 256 output states. > > Did you miss it?
Apparently. -- Rick
On 4/17/2015 1:43 PM, John Larkin wrote:
> On Thu, 16 Apr 2015 23:14:35 -0500, John Fields > <jfields@austininstruments.com> wrote: > >> On Thu, 16 Apr 2015 10:47:36 -0700, John Larkin >> <jlarkin@highlandtechnology.com> wrote: >> >> >>> These are electronics newsgroups. >> >> --- >> And, as such, your narcissistic off-topic garbage has no proper >> place here. >> --- >> >>> We do seem to have a faction of >>> ancient cackling farts who only want to gossip and whine about >>> personalities, and drone out insults, and haven't touched a soldering >>> iron in years, or decades. >> >> --- >> Some of us have progressed past the soldering iron stage > > > Now that's really sad. What do you do all day, argue and whine on > newsgroups? > > I'm collected some parts and am headed for the Metcal. Whine on!
Pot, meet kettle... -- Rick
On 4/17/2015 7:51 AM, Jasen Betts wrote:
> On 2015-04-16, rickman <gnuarm@gmail.com> wrote: >> On 4/15/2015 7:38 PM, John Fields wrote: >>> On Thu, 02 Apr 2015 17:20:47 -0700, Jim Thompson >>> <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>> >>>> On Thu, 02 Apr 2015 18:52:57 -0500, John Fields >>>> <jfields@austininstruments.com> wrote: >>>> >>>>> On 2 Apr 2015 10:42:50 GMT, Jasen Betts <jasen@xnet.co.nz> wrote: >>>>> >>>>>> On 2015-04-01, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>>> On Thu, 02 Apr 2015 07:26:29 +1000, "David Eather" <eather@tpg.com.au> >>>>>>> wrote: >>>>>>> >>>>>>>> On Thu, 02 Apr 2015 05:14:13 +1000, Jim Thompson >>>>>>>> <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >>>>>>>> >>>>>>>>> On Wed, 01 Apr 2015 15:07:54 -0400, Phil Hobbs >>>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>>>>>> >>>>>>>>>> On 04/01/2015 02:00 PM, Jim Thompson wrote: >>>>>>>>>>> For a simulation situation I need a random number generator with a >>>>>>>>>>> twist... >>>>>>>>>>> >>>>>>>>>>> What I need to simulate is a "random" selection of one-of-16 outputs. >>>>>>>>>>> >>>>>>>>>>> Clock "speed" is 12.5kHz ;-) >>>>>>>>>>> >>>>>>>>>>> Built of 74HCxx parts is preferred... I have a full ensemble of those >>>>>>>>>>> device in my PSpice library. >>>>>>>>>>> >>>>>>>>>>> Thanks in advance. >>>>>>>>>>> >>>>>>>>>>> ...Jim Thompson >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> How random? You could use a 16-bit PRBS made from two HC299 and an >>>>>>>>>> HC86. Feed back Q14 XOR Q13, and tap out four stages to a HC154 demux. >>>>>>>>>> If you need better randomness, use four PRBSes of different length. >>>>>>>>>> >>>>>>>>>> Cheers >>>>>>>>>> >>>>>>>>>> Phil Hobbs >>>>>>>>> >>>>>>>>> I just need semi-random enough to test a fast AGC. >>>>>>>>> >>>>>>>>> ...Jim Thompson >>>>>>>> >>>>>>>> there is a bias with the 8-bit just use the last 4 bit idea. With 255 >>>>>>>> 'clocks' all states but 0000 will occur 16 times while 0000 will only >>>>>>>> appear 15 - the cycle then repeats. The lack of the extra 0000 may cause >>>>>>>> the bias point to continually drift high. >>>>>>> >>>>>>> I was wondering about that myself... I'll see if there's a cure. >>>>>> >>>>>> r=(75*r+74)%65537 visits 0-65535 with no gaps. >>>>>> >>>>>> not that i'd want to build it using 74LS logic. >>>>> >>>>> --- >>>>> But, if you had to, what would it look like, schematic-wise? >>>>> >>>>> John Fields >>>> >>>> <smirk>:-} >>>> >>>> ...Jim Thompson >>> --- >>> Amazing, isn't it? >>> >>> Idiots with opinions post their garbage as if it was holy but post >>> no evidence to support their claims. >> >> I don't know that Jim is an idiot, but I'm not sure this formula is very >> useful to implement in logic easily. The multiply is not too bad and >> the addition is easy. But the modulo operation by 2^16+1 is downright >> hard. I think that is why he is smirking. He knows this is not very >> practical... > > The modulo is easier than the multiply. > > one 16 bit - 7 bit subtract > one 16 bit + 0 bit add with carry.
I'm not following. Are you saying a modulo 65537 operation can be done with two adders? -- Rick
On Fri, 17 Apr 2015 10:43:42 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

>On Thu, 16 Apr 2015 23:14:35 -0500, John Fields ><jfields@austininstruments.com> wrote: > >>On Thu, 16 Apr 2015 10:47:36 -0700, John Larkin >><jlarkin@highlandtechnology.com> wrote: >> >> >>>These are electronics newsgroups. >> >>--- >>And, as such, your narcissistic off-topic garbage has no proper >>place here. >>--- >> >>>We do seem to have a faction of >>>ancient cackling farts who only want to gossip and whine about >>>personalities, and drone out insults, and haven't touched a soldering >>>iron in years, or decades. >> >>--- >>Some of us have progressed past the soldering iron stage > > >Now that's really sad. What do you do all day, argue and whine on >newsgroups? > >I'm collected some parts and am headed for the Metcal. Whine on!
Funny how disdain for insults pours out of one side of your mouth, while insults pour out of the other. John Fields